Speaking in today's Scotland on Sunday, Stuart said: "I've lost eight or nine kilos - 18lbs roughly in old money. It was after seeing we had the white jerseys again this season.
"I think I enjoyed my holiday a bit too much after I got back from New Zealand. I had a couple of weeks of R & R, indulging myself let's say, before I had my shoulder operated on.
"At Dunky Weir's wedding, I had a photo taken with the big box sling on, and I looked a tad on the heavy side. So, I had a look at that 'photie' and thought I had better try and make a difference.
"I'd just felt I was a wee bit heavy over the last couple of years, carrying a bit of weight, so I felt I should try and make a difference," says Stuart, who since trimming down, has set various speed records at Warriors.
"We had a Scotland camp, and the coaches were asking, what are you going to do to make this your best season ever. So, I just took the decision to shed a few pounds and see if that would make a difference. I'm never going to be the biggest and strongest of fellas, so you want to put yourself in the best position possible.
"And if that means being able to run around people, or being able to sidestep them, then shedding some kilos has helped this far."